1. Field of the Invention
This invention relates to fluid loading systems, and more particularly to marine loading arms for transferring the fluid between a floating production vessel and a marine tanker.
2. Description of the Prior Art
The production of oil and gas from offshore wells has developed into a major endeavor of the petroleum industry, and this growth has lead to the development of means for transporting petroleum products from offshore wells to shore based refineries or storage facilities. Many of the wells are being drilled and completed in deep-water locations where the oil fields are too small to justify the work and expense of installing a permanent production/processing platform. In many of these locations a floating production vessel, constructed of a tanker which has been specially modified, is yoked to a single point mooring facility at the oil field. The crude petroleum is transferred from the production vessel to a shuttle tanker which transports the petroleum to shore based storage and/or refinery facilities. In some of the larger fields a similar production vessel is used in order to start production of petroleum while the permanent platforms are being built. In either case the production vessel is secured, bow on, to the single point mooring or to a buoy by mooring lines that permit the vessel to swing freely according to the dictates of wind and current and the shuttle tanker is positioned with its bow adjacent the stern of the production vessel. The tanker may be secured to the production vessel by mooring lines, and/or thrusters may be used to hold the tanker in position near the production vessel during the loading operation.
The production vessel and the tanker move relative to each other during the loading operation due to waves, winds, currents, and the amount of cargo which is transferred into the tanker. The height of the tanker and the height of the production vessel above the water line change as the tanker is being loaded, thus requiring that a flexible or articulated hose be used in this procedure. When flexible hoses are used, a tender is normally required to assist in picking up the hose for connection to the tanker's manifold. Such an arrangement not only requires the use of a tender, but movement of the tanker may cause the flexible hose to be broken. Also, such hoses are bulky, heavy, hard to handle, and require a relatively large crew of workers to make up the connection to the tanker.
What is needed is an articulated loading arm which can be mounted on or near the stern of the production vessel from where it can reach the bow of the tanker, which has means to adequately compensate for relative movement between the tanker and the production vessel, and which is fully counterbalanced in all operating as well as stowed positions.